A parameter set for letters on A4 paper, complying with Finnish standards SFS 2486, 2487 and 2488; suitable for window envelopes with window on the left size in the sizes C5, C65, E5 and E65 (although, because the address window is smaller, for sizes E5 and E65 the address may not fit within the window, but ordinary 3-line address should fit).

The author is Hannu Väisänen.